Sound amplifier



Ailg, 2s ,"1'924; 1,506,393 A. A. THOMAS 50mm AMPLIFIER Original Filed Nov. 16, 1922 INVENTOR Patented Aug. 26, 1924.

UNITED STATES ADOLPH THOMAS, OF NEW YORK, N. Y.

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Original application filed November 16, 1922. Serial No. 601,237. Divided November 19, 1923.

To all whom it may comem:

Be it known that I, ADOLPH A. THOMAS,

a citizen of the United States, and a resident of the city of New York, county and State of New York, have invented new and useful Improvements in Sound Amplifiers, of which the following is a specification.

My invention relates to acoustic devices for amplifying sounds produced by vibratory diaphragms, as in phonographs, telephone receivers, radio receiv'ing'apparatus, and the like. The object of my invention is to produce a sound-amplifier giving im proved tone effects and capable of adjustment to control the quality and volume of the amplified sounds.

The most common form of sound-amplifier in use is a horn or megaphone. Tn fact, this type of amplifier is employed almost universally in phonographs and radio loudspeakers. Everybody familiar with am plifying horns knows that they possess certain inherent objections in reference to tone quality. These objections are best described by saying that horns give out sounds of an unnatural horny quality with consequent loss in clearness. In an endeavor to reduce this defect as much as possible, manufacturers have putin the market a great variety of shapes and sizes of horns constructed of various kinds of materials.

It is known that metal horns produce hard penetrating sounds, which may become particularly ofi'ensive in the higher tones, especially when the vibrations of the diaphragms are of considerable amplitude. This is a common experience. So that, while the tones of a metal horn have volume, they are defective in quality and distinctness.

On the other hand, horns of non-metallic materialsuch as wood, fiber, compressed paper, composition and the like-produce sounds of considerably less volume than corresponding horns of metal. l/Vhile these softer tones may be preferable to the loud sounds of a metal horn when the vibrations of the diaphragm are strong, there is the on jection that a non-metallic horn has little carrying power when the diaphragm vibrations are weak.

Attempts have heretofore been made to damp or weaken the action of phonograph horns by choking back the sounds. This has been done either by partially closing and this application filed Serial No. 675,567.

the mouth of the horn, or by using a damper in the throat of the horn. In either case, the resultant tones are decidedly mufiied or choky and lack the required clearness.

The foregoing and other objections and disadvantages of prior sound-amplifiers are eflectively overcome by the new amplifying device of my invention. Broadly stated, the fundamental idea of my invention involves the use of a plurality of sound chambers constructed to produce different tone effects, so that the resultant tones are a blending of the sounds produced by the individual amplifying chambers. By combining a relatively resonant chamber with a relatively mellow chamber, T secure a resultant tone effect which embodies the acoustic advantages of both chambers. I also provide means for controlling the resultant reproduction of the amplifier by varying the acoustic effect of one or more of the sound chambers.

time of the simplest forms of my invention comprises a metal horn surrounded by non-metallic walls (say, of wood) so arranged as to form a conical or pyramidal sound chamber around the horn. The chamber and the horn are open to the free air at their outer ends. The horn is at its inner end connected with a source of sound, which may be, for instance, a phonograph sound-box, a tel phone receiver or the diaphragm of a radio loudspeaker. By means of properly arranged openings, the sound waves enter both amplifying chambers. The resultant tone of the two chambers is a blending of the sharp resonant tones of the inner metal horn with the mellow tones of the outer wooden chamber. In other words, T may say that the resonant tones of the horn are mellowed by the tones of the surrounding outer chamber, and the mellow tones of this chamber are strengthened by the resonant tones of the horn. My new amplifier thus combines volume with quality.

To vary the result tone eflect of the instrument as desired, it provide means "for readily controlling the relative proportion of sound waves issuing out of each chamber. F or this purpose I employ a valve or shutter arrangement by means of which the travel of sound waves through each chamher is regulated. Assuming, as in the example above cited, that we have an inner metal chamber and an outer wooden chamher, the more sound waves we send through the metal chamber, the stronger becomes the final reproduction. Conversely, the greater the proportion of sound waves that pass through the outer wooden chamber, the more mellow are the resultant tones. This control of the sound-amplifying action of my new apparatus is especially useful in phonographs and radio loudspeakers.

In order to explain my invention fully and clearly, I shall describe in detail the illustrative embodiments shown in the accompanying drawings, in which Fig. 1 is a view in longitudinal cross-section showing a form of amplifier containing my invention, portions of the horns being broken away;

Fig. 2 is a view taken approximately on line 22 of Fig. 1;

Fig. 3 shows a full view, on a smaller scale, of the amplifier shown partially in Fig. 1, the walls of the horns being broken away for clearness;

Fig. 1 is a cross-sectional view showing a modified form of control valve for the sound chambers;

Fig. 5 is a cross-section approximately on line 55 of Fig. 4; and

Fig. 6 is a cross-section approximately on line 66 of Fig; 4, except that the valve is shown turned to close the outer horn.

The amplifier shown in Figs. 1, 2 and 3 comprises an outer horn 1 and an inner horn 2, both mounted on a common support indicated as a whole by C, which may be a single casting. The horns or sound chambers 1 and 2 may be of any suitable form and material to produce different tone effects. For instance, the inner horn 2 may be of metal or other material adapted to give a strong resonant reproduction, while the surrounding horn 1 may be of nonmetallic material to impart a soft mellow quality to the tones. The shape and material of the horns may be varied to obtain any desired combination of difierent tonal characteristics. For convenience, we may assume the outer horn 1 to give a mellow reproduction, and the inner horn 2 a more resonant reproduction. The casting C is provided with an outwardly flaring flange 3 to which is secured the inner end of the outer horn 1 by means of screws 4 or otherwise. Gasting C is formed with a disk 5 and a tubular hub 6 which projects forwardly. The disk 5 has sound passages 7 and the hub 6 is at its inner end provided with sound passages 8. The inner horn 2 is mounted at its inner end on the hub 6 of casting C, and is thus surrounded by and properly spaced from the outer horn 1. The sound passages 7 lead into outer horn 1 and the sound passages 8 lead into the inner horn 2. The relative shapes and sizes of horns 1 and 2 are such that the sound space or chamber S between the two horns is of sufiicient area to permit the free passage of sound waves.

To the casting C is secured a suitable extension 9 by means of which the inner chamber 10 of the casting is connected to a source of sound, which may be the vibratory diaphragm of a telephone receiver, or a phonograph sound box, or a radio loudspeaker, or any other suitable source of sound.

I will now describe the means by which the passage of sound waves into the horns 1 and 2 is readily controlled to prod'uce different tone eifects. ithin the chamber 10 of casting C is mounted a valve, indicated as a whole by V. This valve consists of a disk 11 and a tubular extension 12. Valve disk 11 has openings 13 similar in size and arrangement to the passages 7. In Fig. 2, disk 11 is in position to cover the passages 7 completely, which are therefore indicated in dotted lines. The cylindrical valve portion 12 is at its inner end provided with openings 1 1-, which are substantially similar in size and arrangement to the sound passages 8. In Fig. 2, the valve openings 14 are shown in register with the sound passages 8, so that all of the sound waves entering chamber 10 pass into the inner horn 2.

The controlling valve V is operated from the outside by any suitable means, such as a handle or lever 15, which projects through a slot 16 in the casting. If desired, pins or screws 17, or other means, may be used for positively holding the valve V against axial movement, although the lever 15 will probably be sufiicient for that purpose.

Let us suppose that the inner horn 2 is constructed of a material or shape adapted to give a resonant reproduction, and that the outer horn 1 is of a material or shape which gives a relatively softer or more mellow reproduction. After the handle 15 is moved into the position shown in Figs. 1, 2 and 3 to close the sound passages 7 completely and to open fully the sound passages 8, all the sound waves entering the amplifier pass through the resonant horn 2 and we get a correspondingly loud and sharp reproduction. In Fig. 3 this position of the controlling valve is indicated as vthe loud position. By moving the handle 15 halfway over, as indicated by the dotted lines 15 in Fig. 2, the sound passages 7 and 8 are approximately half-way open (roughly indicated by dotted lines 7 and 8 in Fig. 2) and the sound waves entering the amplifier pass into the free air partly through the mellow outer horn 1 and partly through the resonant inner horn 2. The resultant tone effect is a blending of the acoustic ac tion of the two horns and gives a more mellow reproduction than horn 2 alone would give, and a more resonant reproduction than could be obtained with horn 1 alone. By moving the handle 15 to the extreme right position (as viewed in Fig. 2), the sound passages 8 are entirely closed and the sound passages 7 are open in full, so that all the sound passes through the outer horn 1 into the free air.' This produces a still more mellow tone effect. It is clear that by adjusting the valve handle 15 in difl'erent intermediate posit-ions, diderent tone effects will be produced.

Figs. 4, 5 and 6 show a construction similar to Figs. 1, 2 and 3, except that the controlling valve is slightly ditlerent in form, although it is precisely the same in operation as the previously described vali e V. Referring in detail to the last three figures, we have a suitable casting or support C carrying an outer horn 1 and an inner horn 2, which are secured to the casting in the same way as horns 1 and 2 previously referred to. One of these horns (say, for example, the outer horn 1) is constructed of a material or shape adapted to give a comparatively mellow reproduction, and the other horn (in that case horn 2') is of a material or shape which gives a more resonant reproduction. The casting C has a cylindrical hub 18 provided with a set of sound passages 19 and another set of sound passages 20. As seen from Fig. 4, the sound passages'l9 lead into the outer horn 1 and the sound passages 20 communicate with the inner horn 2. Within the hub 18 is mounted a cylindrical valve V having a set of openings 21 and another set of openings 22. Valve openings 21 are adapted to control the sound passages 19, and valve openings 22 are arranged to control the sound passages 20. The valve V is controlled from the outside by any suitable means, such as a handle 23, which projects through a slot 24 in the casting C. In Figs. 4: and 5, the valve V is in position to close the sound openings 20' and open the sound openings 19, so that all the sound waves pass through the outer horn 1', which we have assumed to be the more mellow sound chamber. The valve is, thus in what we may call the soft position, as'indicated in Fig. 5. By throwing the handle 23 over into the loud posltion, the outer horn is closed and the inner horn is fully opened to the sound waves, with the result that we get a stronger reproduction. Any intermediate position opens the sound passages through both horns, so that the relative proportron of sound waves issuing out of the horns may be controlled as desired.

In Figs 3 and 4, the inner horns 2 and 2' may, if desired, be provided with. lateral openings indicated by dotted lines 25. In that case, the sound waves would always issue out of both horns, but valve V or V would operate just the same to control the relative proportion of sound waves passing through the horns.

The amplifiers above described may be used in radio loudspeakers by simply inserting them in the base of the loudspeaker unit, as will be understood, or they may be embodied in phonograph cabinets. In the latter case, the tone-controlling valve could be operated from the side of simply attaching a rod to the end of handle 15 or 23, as will be readily understood.

Attention is called to the fact that the tone-controlling device of my invention is not a choking orthrottling damper; rather is it a valve for shifting or deflecting the passage of sound waves through the horns in varying proportions. Consequently, my controlling mechanism does not produce the choky effect of the horn dampers previously employed.

llt will be apparent from the foregoing explanation that my new sound-amplifier with its sound chambers of different tone effects gives better reproduction than prior devices employing a single horn or chamber. Furthermore, by means of the tone valve, the amplifying action of my device is readily controlled by the operator to produce any tone eflect within the limits of the instrument. In the matter of construction, my new amplifier is remarkably simple and easy to make, besides being compact in the arrangement of parts.

The amplifier of my invention possesses special advantages for radio reception, where broadcast programs vary from the reporting of sporting events to the rendition of vocal or instrumental solos. An amplifier adapted to give the best reproduction of speech does not usually give the best results in reproducing music or song, and vice versa. For instance, it has been found that in reproducing announcements of sporting events in a large hall, a loud-speaker with a high resonant pitch is more satisfactory than one emitting low rumbling tones, which lack clearness. On the other hand, a piano solo is best reproduced with an, amplifier having mellow tonal, characteristics. Now, my new amplifier may be so regulated in its tone reproduction as to give the best results in the reproduction of any kind of broad-casting. In other words, the amplifier of my invention embodies a plurality of amplifiers in a single instrument.

Although l have herein shown and described certain specific constructions, it is clear that the broad idea of my invention may be mechanically embodied in other ways. The size, shape and material of the horns or sound chambers may be varied in accordance with the particular tone efiects and relative arrangement of the horns may be varied to suit particular circumstances or the cabinet by .desired to be produced. Also, the number a The walls of the sound chambers should be to effect certain results. While I have spoken of the inner horns as the resonant sound chambers and of the outer horns as the more mellow sound chambers, it is obvious that the outer horns may be constructed to give more resonance than the inner horns. The difference in tone'effects between the various sound chambers may be brought about not only by the use of difierent materials, as already mentioned, but by variations in size and shape of the horns, even with the same material. Nor is it necessary that the horns are nested, as shown, although that arrangement is desirable from a practical standpoint on account of the resulting compactness. When I refer. to nested horns or sound chambers in the de scription and claims, I do not mean that they shall be concentrically mounted, but I include any arrangement in which the smaller chamber is within the casing of the larger chamber. In the broader aspectof my invention, the inner horn may be regarded as a wall within the casing formed by the walls of the larger chamber and dividing said easing into two sound chambers of different tonal characteristics.

It is preferable to support the horns independently of each other, for any direct connection between the horns, such as spacing rods, would cause the vibrations of one horn to be communicated to the other, thereby injuring the quality of reproduction.

smooth and rigid for the best results.

When I speak of the horn support C or C as a casting, I use the term as a convenience to indicate a supporting member which may be cast or molded in a single piece or built up out of several parts. Furthermore, this supporting member may be of any suitable material, metallic or non-metallic. Also, in referring to the member V or V as a valve, I use the expression in a broad sense to mean any practical device to control the passage of sound waves through the am plifying horns or chambers. For brevity, I have designated the amplifying members 1 and 2 (or 1 and 2') as horns, by which.

I mean an practical shape or form of sound cham er.

I do not herein claim broadly a sound amplifier comprising a plurality of sound chambers constructed to produce different tone effects and having means for controlling the resultant tone quality by regulating the relative proportion of sound waves passing simultaneously through the amplifying chambers, because that is covered in my copending application Serial Number 601,237, filed November 16, 1922, and now Patent No. 1,481,634, dated January 22, 1924. The presentapplication is a division of said co- .pending case, and was filed to avoid an official requirement of division.

I claim as my invention:

1. A sound amplifier comprising a plurality of nested sound chambers constructed to produce different tone effects, a support for the inner ends of said nested chambers, and adjustable means on said support for controlling the relative proportion of sound waves issuing simultaneously out of said chambers.

2. A sound amplifier comprising a plurality of nested sound chambers constructed toproduce different tone effects, a tubular member arranged axially at the inner ends of said nested chambers for connecting said chambers with a source of sound, and a valve mounted on said member for controlling the relative proportion of sound waves issuing simultaneously out of said chambers.

3. In a sound-amplifier, the combination with a pair of nested horns adapted to be connected with a source of sound, of a rotatable valve at the inner ends of said horns for regulating the passage of sound waves simultaneously through both horns.

4. A sound amplifier comprising a pair of nested horns open to the free air at their outer ends, means providing an opening for each horn to connect the same at its inner end with a source of sound, and means for varying the effective areas of said openings to control the relative proportion of sound waves issuing out of said horns.

5. A sound amplifier comprising a plurality of nested sound chambers, and means at the inner ends of said nested chambers for controlling the relative proportion of said waves passing simultaneously through said chambers.

6. A sound amplifier comprising a plurality of sound chambers constructed to produce different tone effects, and a rotary valve at the inner ends of said chambers for con trolling the relative proportion of sound waves passing simultaneously through said chambers.

7. A sound amplifier comprising a plurality of nested horns, and a tubular valve mounted at the inner ends of said horns substantially in axial alignment with the axes of said horns.

8. In a sound amplifier, a support provided with a passage adapted to be connected with a source of sound, said support having two sets of sound openings leading out of said passage, a horn connected to said support so as to communicate with one set of sound openings, walls connected to said casting to form an outwardly diverging sound chamber around said horn, said chamber communicating with the otherset of sound openings, and a valve for controlling both sets of openings.

9. In a sound amplifier, a support provided with a passage adapted to .be connected with a source of sound, said support vided with a neoaeea havin two sets of sound openings leading out oi said passage, a horn connected to said support so as to communicate with one set of sound openings, walls connected to said support to form an outwardly diverging sound chamber around said horn, said chamber communicating with the other set of sound openings, ly controlling both sets of openings.

10. In a sound amplifier, a support procentral tubular portion and a surrounding flanged portion, a horn con nected at its inner end to said tubular portion, diverging walls arranged toi orm a sound chamber around said horn and secured at their inner end to said flanged portion, means for connecting said horn and said surrounding chamber with a source of sound, and a valve on said support for controlling the relative proportion of sound waves issuing out of said horn and out of said chamber.

11. In a sound amplifier, vided with a central tubular surrounding flanged portion, nected at its inner a support proportion and a a horn con end to said tubular portion, said tubular portion being adapted to be connected with a source or" sound and having sound passages leading into said horn, diverging Walls arranged to form a sound chamber around said horn and secured at their inner end to said flanged portion, said support having sound passages leading into said surrounding chamber, and means for and means for simultaneousconnecting controlling said two sets of sound passages. 12. In a sound amplifier, a casting comprising a main tubular section provided between its ends with a surrounding flange, one end of said tubular section beingadapted to be connected with a source of sound, a horn having its inner end slipped over the other end of said tubular section, diverging walls arranged to form a sound chamber around said horn and secured at their inner ends to said flange, the axis of said tubular section being substantially coincident with the axes of said horn and said surrounding chamber, said tubular section having sound openings leading respectively to said chamber andsaid horn, and a valve in said tubular section for controlling said sound openings to vary the relative proportion of sound waves passing throughsaid horn and said chamber, t

13., A sound amplifier comprising walls arranged to form a diverging casing, a wall mounted within said casing to divide the same into two outwardly diverging sound chambers of diiierent tonal characteristics, said chambers being open at the larger outer ends for the emisslon of sound, means for the inner ends of said chambers with a source of sound, and a valve at the inner ends of said chambers for controlling the relative proportion of sound waves passan ing simultaneously through said chaI'nbers.

ADULPl-ll A. THOMAS, 

